MAGNETIC DRUM TRANSLATOR FOR TOLL SWITCHING OFFICES 731 



Fig. 9 — Magnetic head and mounting bracket showing means of adjustment. 



I 



The magnetic structure is assembled on a nickel-silver plate to which 

 have been soldered two copper shoes which serve to locate the pole pieces 

 and shield the pole-tips, thereby focusing the recording flux to some de- 

 gree. After adjustment of the pole-tips, the assembly is clamped in a 

 I sandwich by means of a second, smaller nickel-silver plate. As is evident 

 i from the illustration, this magnetic assembly is in turn assembled to a 

 mounting bracket which contains facilities for precisely adjusting the 

 clearance between pole-tips and drum surface. 



The pole- tips of the head are 0.050" wide and the tracks are on 0.10'' 

 centers, leaving a nominal value of 0.050" between tracks to allow for 

 misalignment of heads and for flux-spreading. Heads which are physi- 

 i cally adjacent in each of the four corner stacks are mounted on 0.40" 

 centers, but the stacks are offset with respect to one another, thereby 

 interlacing the tracks on the drum. 



The read-write heads have been designed expressly for use in liigh- 

 speed digital recording. Very thin laminations are used and this, coupled 

 with carefully prescribed manufacturing techniques, results in a head 

 having a satisfactory frequency response for the very short pulses em- 

 ployed. When used as a transducer to convert electrical pulses to mag- 



